Tire innerliner composition

ABSTRACT

A composition suitable for use in producing a tire innerliner is provided. The composition comprises a halogen-containing copolymer of a C 4  to C 7  isomonoolefin and a para-alkylstyrene; carbon black, and a plasticizer oil. A vulcanized tire comprising an innerliner made from the composition is also provided.

This is a division, of application Ser. No. 07/917,556, filed Jul. 21,1992, now U.S. Pat. No. 5,333,662, which is a continuation ofapplication Ser. No. 07/840,675, filed Feb. 21, 1992, now abandoned,which is a continuation of application Ser. No. 07/554,747, filed Jul.18, 1990 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a composition for use in tireinnerliners, particularly in tires for motor vehicles.

2. Description of Information Disclosures

The use of butyl rubber and halogenated butyl rubber, to produceinnerliners for rubber tires is known. See, for example, U.S. Pat. No.2,943,664.

Although there are many commercially available tire innerliners whichare impermeable to air, there is still a need to improve the propertiesof innerliners, such as heat aging performance, while maintainingadhesive strength.

It has now been found that a tire innerliner that is made from acomposition comprising certain halogen- containing copolymers of a C₄ toC₇ isomonoolefin and a para-alkylstyrene has improved properties, suchas, for example, improved heat aging resistance, particularly for agedflex resistance, tensile strength, and elongation at break, whilemaintaining low air permeability properties.

SUMMARY OF THE INVENTION

In accordance with the invention, there is provided a tire innerlinercomposition comprising: (a) a halogen-containing copolymer of a C₄ to C₇isomonoolefin and a para-alkylstyrene, (b) carbon black; (c) aplasticizer oil; and (d) a curing agent.

In accordance with the invention, there is also provided a vulcanizedtire comprising an innerliner, at least a portion of said innerlinerbeing made of a composition comprising: (a) a halogen-containingcopolymer of a C₄ to C₇ isomonoolefin and a para-alkylstyrene, (b)carbon black; and (c) a plasticizer oil.

DETAILED DESCRIPTION OF THE INVENTION

The tire innerliner composition of the present invention comprises ahalogen-containing copolymer of a C₄ to C₇ isomonoolefin and apara-alkylstyrene, carbon black, a plasticizer oil, and a curing agentwith or without curing agent accelerators. Optionally, the compositionmay comprise fillers other than the carbon black and rubber compoundingadditives.

Suitable halogen-containing copolymers of a C₄ to C₇ isomonoolefin and apara-alkylstyrene for use as a component of the present tire innerlinercomposition comprise at least 0.5 weight percent of thepara-alkylstyrene moiety. For elastomeric copolymer products, thepara-alkylstyrene moiety may range from about 0.5 weight percent toabout 20 weight percent, preferably from about 5 to about 20 weightpercent, more preferably from about 2 to about 20 weight percent of thecopolymer. The halogen content of the copolymers may range from abovezero to about 7.5 weight percent. The halogen may be bromine, chlorine,and mixtures thereof. Preferably, the halogen is bromine. The majorportion of the halogen is chemically bound to the para-alkyl group, thatis, the halogen-containing copolymer comprises para-halo alkyl groups.

The copolymers of the isomonoolefin and para-alkylstyrene useful toprepare the halogen-containing copolymers suitable as component of thetire innerliner composition of the present invention include copolymersof isomonoolefin having from 4 to 7 carbon atoms and apara-alkylstyrene, such as those described in European patentapplication 89305395.9 filed May 26, 1989, (Publication No. 0344021published Nov. 29, 1989). The preferred isomonoolefin comprisesisobutylene. The preferred para-alkylstyrene comprisespara-methylstyrene. Suitable copolymers of an isomonoolefin and apara-alkylstyrene include copolymers having a number average molecularweight (Mn) of at least about 25,000, preferably at least about 30,000,more preferably at least about 100,000. The copolymers also, preferably,have a ratio of weight average molecular weight (Mw) to number averagemolecular weight (Mn), i.e., Mw/Mn of less than about 6, preferably lessthan about 4, more preferably less than about 2.5, most preferably lessthan about 2. The brominated copolymer of the isoolefin andpara-alkylstyrene obtained by the polymerization of these particularmonomers under certain specific polymerization conditions now permit oneto produce copolymers which comprise the direct reaction product (thatis, in their as-polymerized form), and which have unexpectedlyhomogeneous uniform compositional distributions. Thus, by utilizing thepolymerization and bromination procedures set forth herein, thecopolymers suitable for the practice of the present invention can beproduced. These copolymers, as determined by gel permeationchromatography (GPC) demonstrate narrow molecular weight distributionsand substantially homogeneous compositional distributions, orcompositional uniformity over the entire range of compositions thereof.At least about 95 weight percent of the copolymer product has apara-alkylstyrene content within about 10 wt. percent, and preferablywithin about 7 wt. percent, of the average para-alkylstyrene content forthe overall composition, and preferably at least about 97 wt. percent ofthe copolymer product has a para-alkylstyrene content within about 10wt. percent and preferably within about 7 wt. percent, of the averagepara-alkylstyrene content for the overall composition. Thissubstantially homogeneous compositional uniformity thus particularlyrelates to the intercompositional distribution. That is, with thespecified copolymers, as between any selected molecular weight fraction,the percentage of para-alkylstyrene therein, or the ratio ofpara-alkylstyrene to isoolefin, will be substantially the same, in themanner set forth above.

In addition, since the relative reactivity of para-alkylstyrene withisoolefin such as isobutylene is close to one, the intercompositionaldistribution of these copolymers will also be substantially homogeneous.That is, these copolymers are essentially random copolymers, and in anyparticular polymer chain the para-alkylstyrene and isoolefin units willbe essentially randomly distributed throughout that chain.

The halogen-containing copolymers useful in the practice of the presentinvention have a substantially homogeneous compositional distributionand include the para-alkylstyrene moiety represented by the formula:##STR1## in which R and R¹ are independently selected from the groupconsisting of hydrogen, alkyl preferably having from 1 to 5 carbonatoms, primary haloalkyl, secondary haloalkyl preferably having from 1to 5 carbon atoms, and mixtures thereof and x is selected from the groupconsisting of bromine, chlorine and mixtures thereof, such as thosedisclosed in European patent application 8930595.9 filed May 26, 1989,(Publication No. 0344021 published Nov. 29, 1989).

Various methods may be used to produce the copolymers of isomonoolefinand para-alkylstyrene, as described in said European publication.Preferably, the polymerization is carried out continuously in a typicalcontinuous polymerization process using a baffled tank-type reactorfitted with an efficient agitation means, such as a turbo mixer orpropeller, and draft tube, external cooling jacket and internal coolingcoils or other means of removing the heat of polymerization, inlet pipesfor monomers, catalysts and diluents, temperature sensing means and aneffluent overflow to a holding drum or quench tank. The reactor ispurged of air and moisture and charged with dry, purified solvent or amixture of solvent prior to introducing monomers and catalysts.

Reactors which are typically used in butyl rubber polymerization aregenerally suitable for use in a polymerization reaction to produce thedesired para-alkylstyrene copolymers suitable for use in the process ofthe present invention. The polymerization temperature may range fromabout minus 35° C. to about minus 100° C., preferably from about minus40° to about minus 80° C.

The processes for producing the copolymers can be carried out in theform of a slurry of polymer formed in the diluents employed, or as ahomogeneous solution process. The use of a slurry process is, however,preferred, since in that case, lower viscosity mixtures are produced inthe reactor and slurry concentration of up to 40 wt. percent of polymerare possible.

The copolymers of isomonoolefins and para-alkylstyrene may be producedby admixing the isomonoolefin and the para-alkylstyrene in acopolymerization reactor under copolymerization conditions in thepresence of a diluent and a Lewis acid catalyst.

Typical examples of the diluents which may be used alone or in a mixtureinclude propane, butane, pentane, cyclopentane, hexane, toluene,heptane, isooctane, etc., and various halohydrocarbon solvents which areparticularly advantageous herein, including methylene, chloride,chloroform, carbon tetrachloride, methyl chloride, with methyl chloridebeing particularly preferred.

An important element in producing the copolymer is the exclusion ofimpurities from the polymerization reactor, namely, impurities which, ifpresent, will result in complexing with the catalyst or copolymerizationwith the isomonoolefins or the para-alkylstyrene, which in turn willprevent one from producing the para-alkylstyrene copolymer productuseful in the practice of the present invention. Most particularly,these impurities include the catalyst poisoning material, moisture andother copolymerizable monomers, such as, for example,metal-alkylstyrenes and the like. These impurities should be kept out ofthe system.

In producing the suitable copolymers, it is preferred that thepara-alkylstyrene be at least 95.0 wt. percent pure, preferably 97.5 wt.percent pure, most preferably 99.5 wt. percent pure and that theisomonoolefin be at least 99.5 wt. percent pure, preferably at least99.8 wt. percent pure and that the diluents employed be at least 99 wt.percent pure, and preferably at least 99.8 wt. percent pure.

The most preferred Lewis acid catalysts are ethyl aluminum dichlorideand preferably mixtures of ethyl aluminum dichloride with diethylaluminum chloride. The amount of such catalysts employed will depend onthe desired molecular weight and the desired molecular weightdistribution of the copolymer being produced, but will generally rangefrom about 20 ppm to 1 wt. percent and preferably from about 0.001 to0.2 wt. percent, based upon the total amount of monomer to bepolymerized.

Halogenation of the polymer can be carried out in the bulk phase (e.g.,melt phase) or either in solution or in a finely dispersed slurry. Bulkhalogenation can be effected in an extruder, or other internal mixer,suitably modified to provide adequate mixing and for handling thehalogen and corrosive by-products of the reaction. The details of suchbulk halogenation processes are set forth in U.S. Pat. No. 4,548,995.

Suitable solvents for solution halogenation include the low boilinghydrocarbons (C₄ to C₇) and halogenated hydrocarbons. Since the highboiling point para-methylstyrene makes its removal by conventionaldistillation impractical, and since it is difficult to avoid completelysolvent halogenation, it is very important where solution or slurryhalogenation is to be used that the diluent and halogenation conditionsbe chosen to avoid diluent halogenation, and that residualpara-methylstyrene has been reduced to an acceptable level.

With halogenation of para-methylstyrene/isobutylene copolymers, it ispossible to halogenate the ring carbons, but the products are ratherinert and of little interest. However, it is possible to introducehalogen desired functionality into the paramethylstyrene/isobutylenecopolymers hereof in high yields and under practical conditions withoutobtaining excessive polymer breakdown, cross-linking or otherundesirable side reactions.

It should be noted that radical bromination of the enchained para-methylstyryl moiety in the useful copolymers for the practice of thisinvention can be made highly specific with almost exclusive substitutionoccurring on the para-methyl group, to yield the desired benzylicbromine functionality. The high specificity of the bromination reactioncan thus be maintained over a broad range of reaction conditions,provided, however, that factors which would promote the ionic reactionroute are avoided (i.e., polar diluents, Friedel-Crafts catalysts,etc.).

Thus, solutions of the suitable para-methylstyrene/isobutylenecopolymers in hydrocarbon solvents such as pentane, hexane or heptanecan be selectively brominated using light, heat, or selected radicalinitiators (according to conditions, i.e., a particular radicalinitiator must be selected which has an appropriate half-life for theparticular temperature conditions being utilized, with generally longerhalf-lives preferred at warmer hydrogenation temperatures) as promotersof radical halogenation, to yield almost exclusively the desiredbenzylic bromine functionality, via substitution on the para-methylgroup, and without appreciable chain scission and/or cross-linking.

This reaction can be initiated by formation of a bromine atom, eitherphotochemically or thermally (with or without the use of sensitizers),or the radical initiator used can be one which preferentially reactswith a bromine molecule rather than one which reacts indiscriminatelywith bromine atoms, or with the solvent or polymer (i.e., via hydrogenabstraction). The sensitizers referred to are those photochemicalsensitizers which will themselves absorb lower energy photons anddisassociate, thus causing, in turn, disassociation of the bromine,including materials such as iodine. It is, thus, preferred to utilize aninitiator which has a half life of between about 0.5 and 2500 minutesunder the desired reaction conditions, more preferably about 10 to 300minutes. The amount of initiator employed will usually vary between 0.02and 1 percent by weight on the copolymer, preferably between about 0.02and 0.3 percent. The preferred initiators are bis azo compounds, such asazo bis isobutyronitrile (AIBN), azo bis (2,4 dimethyl valero) nitrile,azo bis (2 methyl butyro) nitrile, and the like. Other radicalinitiators can also be used, but it is preferred to use a radicalinitiator which is relatively poor at hydrogen abstraction, so that itreacts preferentially with the bromine molecules to form bromine atomsrather than with the copolymer or solvent to form alkyl radicals. Inthose cases, there would then tend to be resultant copolymer molecularweight loss, and promotion of undesirable side reactions, such ascross-linking. The radical bromination reaction of the copolymers ofpara-methylstyrene and isobutylene is highly selective, and almostexclusively produces the desired benzylic bromine functionality. Indeed,the only major side reaction which appears to occur is disubstitution atthe para-methyl group, to yield the dibromo derivative, but even thisdoes not occur until more than about 60 percent of the enchainedpara-methylstyryl moieties have been monosubstituted. Hence, any desiredamount of benzylic bromine functionality in the monobromo form can beintroduced into the above stated copolymers, up to about 60 mole percentof the para-methylstyrene content.

It is desirable that the termination reactions be minimized duringbromination, so that long, rapid radical chain reactions occur, and sothat many benzylic bromines are introduced for each initiation, with aminimum of the side reactions resulting from termination. Hence, systempurity is important, and steady-state radical concentra- tions must bekept low enough to avoid extensive recom- bination and possiblecross-linking. The reaction must also be quenched once the bromine isconsumed, so that continued radical production with resultant secondaryreactions (in the absence of bromine) do not then occur. Quenching maybe accomplished by cooling, turning off the light source, adding dilutecaustic, the addition of a radical trap, or combinations thereof.

Since one mole of HBr is produced for each mole of bromine reacted withor substituted on the enchained para-methylstyryl moiety, it is alsodesirable to neutralize or otherwise remove this HBr during thereaction, or at least during polymer recovery in order to prevent itfrom becoming involved in or catalyzing undesirable side reactions. Suchneutralization and removal can be accomplished with a post-reactioncaustic wash, generally using a molar excess of caustic on the HBr.Alternatively, neutralization can be accomplished by having aparticulate base (which is relatively nonreactive with bromine) such ascalcium carbonate powder present in dispersed form during thebromination reaction to absorb the HBr as it is produced. Removal of theHBr can also be accomplished by stripping with an inert gas (e.g., N₂)preferably at elevated temperatures.

The brominated, quenched, and neutralized para-methylstyrene/isobutylenecopolymers can be recovered and finished using conventional means withappropriate stabilizers being added to yield highly desirable andversatile functional saturated copolymers.

In summary, halogenation to produce a copolymer useful in the presentinvention is preferably accomplished by halogenating anisobutylene-para-methylstyrene copolymer using bromine in a normalalkane (e.g., hexane or heptane) solution utilizing a bis azo initiator,e.g., AIBN or VAZO® 52: 2,2'-azobis(2,4-dimethylpentane nitrile), atabout 55° to 80° C., for a time period ranging from about 4.5 to about30 minutes, followed by a caustic quench. The recovered polymer iswashed in basic water wash and water/isopropanol washes, recovered,stabilized and dried.

In addition to the halogen-containing copolymer of a C₄ to C₇isomonoolefin and a para-alkylstyrene, the tire innerliner compositionof the present invention also comprises carbon black, a plasticizer oil,and a curing agent. Optionally, the composition may comprise a rubbercomponent of certain rubbers other than the halogen-containing copolymerof a C₄ to C₇ isomonoolefin and the para-alkylstyrene.

Suitable optional rubber components for the composition of the presentinvention, in addition to the halogen-containing copolymer of theisomonoolefin and the para-alkylstyrene, are rubbers selected from thegroup consisting of natural rubber, styrene-butadiene rubber,polybutadiene rubber, a terpolymer of ethylene, propylene, and anonconjugated diene (EPDM), and mixtures thereof. The additionaloptional rubber component may be an oil extended rubber of thesesuitable rubbers.

Furthermore, the tire innerliner composition may, optionally, comprise acomponent selected from the group consisting of a filler other thancarbon black, a rubber compounding additive and mixtures thereof. Thecarbon black may be derived from any source. Suitable carbon blackincludes channel black, furnace black, thermal black, acetylene black,lamp black and the like. The filler and/or additive may be anyconventional filler and/or additive generally used with rubber.

Suitable plasticizer oils include hydrocarbon plasticizer oils such asparaffinic, naphthenic or aromatic petroleum oils. The preferredplasticizer oil is a paraffinic petroleum oil. Suitable hydrocarbonplasticizer oils include oils having the following generalcharacteristics:

    ______________________________________                                        Property    Preferred    Minimum   Maximum                                    ______________________________________                                        API° gravity at                                                                    15-30        10        35                                         60° F.                                                                 (15.5° C.)                                                             Flash Point, °F.                                                                   330-450      300       700                                        (open cup method)                                                                         (165-232° C.)                                                                       (148° C.)                                                                        (371° C.)                           Pour Point, °F.                                                                    -30 to +30   -35       60                                                     (-34 to -1° C.)                                                                     (-37° C.)                                                                        (15° C.)                            SSU at 100° F.                                                                       100-7,000  50        20,000                                     (38° C.)                                                               ______________________________________                                    

The optional other filler may be a non-reinforcing filler, a reinforcingfiller, an organic filler, and an inorganic filler, or mixtures thereof.

Suitable fillers, other than carbon black, include calcium carbonate,clay, silica, talc, titanium dioxide and mixtures thereof. Suitablerubber compounding additives include antioxidants, stabilizers, rubberprocessing aids, pigments and mixtures thereof. The rubber processingaids may be an oil such as paraffinic, naphthenic, or aromaticprocessing oils. Suitable antioxidants include hindered phenols, aminophenols, hydroquinones, certain amine condensation products and thelike. The preferred additives are fatty acids, low molecular weightpolyethylene, waxes and mixtures thereof. A preferred fatty acid isstearic acid. Mixtures of other fatty acids can be used with the stearicacid.

The tire innerliner composition of the present invention also comprisesa curing agent.

Suitable curing agents include peroxide cures, elemental sulfur cures,sulfur-containing compound cures, and non-sulfur cures. For example, thecuring agent may be zinc oxide. Optionally, curing agent acceleratorsmay be used such as dithiocarbamates, thiurams, thioureas, and mixturesthereof; zinc oxide-free cures may also be used such as, for example,litharge, 2-mercaptoimidazoline, and diphenyl guanidine;2-mercaptobenzimidazole, and N,N'-phenylene-bismaleimide. Organicperoxide may be used as curing agents, such as, for example, dicumylperoxide, benzoyl peroxide, A,A'-Bis(tertiary butyl peroxy) diisopropylbenzene, and the like. Accelerator activators may also be used.

A preferred curing system comprises zinc oxide, sulfur and2,2'-benzothiazyl disulfide (MBTS) accelerator.

The tire innerliner composition of the present invention may comprisethe halogen-containing copolymer of a C₄ to C₇ isomonoolefin and apara-alkylstyrene in an amount ranging from about 40 to about 70,preferably from about 45 to about 65 weight percent, the carbon black inan amount ranging from about 20 to about 45, preferably from about 25 toabout 40 weight percent; the plasticizer oil in an amount ranging fromabove zero to about 25, preferably from about 5 to about 20 weightpercent; the total amount of other fillers and additives in an amountranging from above zero to about 50, preferably from above zero to about20 weight percent; and the curing agent in an amount ranging from about1 to 6, preferably from about 1 to 3 weight percent, all saidpercentages being based on the weight of the total composition.

If other optional rubbers are present, the weight percent of thehalogen-containing copolymer is adjusted in such a way that the totalrubber content of the composition may fall within the range of 40 to 70weight percent, preferably 45 to 65 weight percent of the totalcomposition. In the embodiment in which one or more optional additionalrubbers are present in the composition, it is preferred that thehalogen-containing copolymer of an isomonoolefin and para-alkystyrene bepresent in an amount of at least about 50 weight percent of the totalrubber content, that is, of said halogen-containing copolymer plus theoptional additional rubbers.

The tire innerliner composition of the present invention may bevulcanized by subjecting it to heat according to any conventionalvulcanization process. Typically, the vulcanization is conducted at atemperature ranging from about 100° C. to about 250° C., preferably fromabout 150° C. to about 200° C., for a time period ranging from about 1minute to several hours.

The tire innerliner composition of the present invention may be used inproducing innerliners for tires, for example, motor vehicle tires suchas truck tires, bus tires, passenger automobile, motorcycle tires, andthe like. The improved heat aging resistance of the present compositionmakes it particularly suited for use in truck tires to increase theretreading capability of the tire.

Suitable tire innerliner compositions may be prepared by usingconventional mixing techniques including, e.g., kneading, rollermilling, extruder mixing, internal mixing (such as with a Banbury®mixer), etc. The sequence of mixing and temperatures employed are wellknown to the skilled rubber compounder, the objective being thedispersion of fillers, activators and curatives in the polymer matrixwithout excessive heat buildup. A useful mixing procedure utilizes aBanbury mixer in which the copolymer rubber, carbon black andplasticizer are added and the composition mixed for the desired time orto a particular temperature to achieve adequate dispersion of theingredients. Alternatively, the rubber and a portion of the carbon black(e.g., one-third to two-thirds) is mixed for a short time (e.g., about 1to 3 minutes) followed by the remainder of the carbon black and oil.Mixing is continued for about 5 to 10 minutes at high rotor speed duringwhich time the mixed components reach a temperature of about 140° C.Following cooling, the components are mixed in a second step on a rubbermill or in a Banbury mixer during which the curing agent and optionalaccelerators, are thoroughly and uniformly dispersed at relatively lowtemperature, e.g., about 80° to about 105° C. Variations in mixing willbe readily apparent to those skilled in the art and the presentinvention is not limited to any specific mixing procedure. The mixing isperformed to disperse all components of the composition thoroughly anduniformly.

The innerliner composition is formed, typically, into a sheet, such asby calendering. The sheet may then be placed adjacent to an intermediatelayer (e.g., carcass layer) of an uncured tire which is being formed ona tire building drum. Tires are generally built on a drum from at leastthree layers, namely, an outer layer, an intermediate layer, and aninner layer (e.g., innerliner). After the uncured tire has been built ona building drum, the uncured tire may be placed in a heated mold toshape it and heat it to vulcanization temperatures and, thereby, toproduce a cured unitary tire from the multi-layers.

Vulcanization of a molded tire, typically, is carried out in heatedpresses under conditions well known to those skilled in the art.

Curing time will be affected by the thickness of the tire to be moldedand the concentration and type of curing agent as well as the halogencontent of the halogenated copolymer. However, the vulcanizationparameters can readily be established with a few experiments utilizinge.g., a laboratory characterization device well known in the art, theMonsanto Oscillating Disc Cure Rheometer (ODR, described in detail inAmerican Society for Testing and Materials, Standard ASTM D 2084).

The following examples are presented to illustrate the invention. Allparts and percentages herein are by weight unless specifically otherwiseindicated.

EXAMPLE

Experiments were performed to compare compositions in accordance withthe present invention with a composition comprising a bromobutyl rubberin a tire innerliner type formulation. The results of these experimentsare summarized in Tables I, II, III and IV. In these tables, compositionA and B were compositions in accordance with the present invention.Composition C was not a composition in accordance with the presentinvention.

Copolymer Z was a brominated isobutylene-para-methylstyrene copolymercomprising 1.9 wt. % bromine and 5 wt. % para-methylstyrene moieties.

Copolymer Y was a brominated isobutylene-para-methylstyrene copolymercomprising 1.9 wt. % bromine and 10 wt. % para-methylstyrene moieties.

Copolymer X was Exxon bromobutyl rubber grade 2222 comprising 2 wt. %bromine.

Compositions A through C were compounded using a laboratory internalmixer. The mix cycle used is shown in Table I. The test methods used areshown in Table V.

                  TABLE I                                                         ______________________________________                                                      COMPOSITION                                                     Ingredients     A         B       C                                           ______________________________________                                        Copolymer Z     100                                                           Copolymer Y               100                                                 Copolymer X                       100                                         Carbon Black N-660                                                                            60        60      60                                          FLEXON 876.sup.(1)                                                                            15        15      15                                          STEARIC ACID    1         1       1                                           ZnO             2         2       3                                           SULPHUR         1         1         0.5                                       MBTS.sup.(2)    2         2         1.5                                       FORMULA WEIGHT  181       181     181                                         SPEC GRAVITY      1.11      1.11    1.11                                      ______________________________________                                        Mixing cycle    Conventional Mixing Cycle                                     ______________________________________                                        0.0':Polymer,Black.                                                           Loading         1.600 L                                                       1.5':Oil,Stearic Acid.                                                        1 or 2 passes   2 passes                                                      3.0':Cleaning                                                                 Dump temp °C.                                                                          140° C./add curative on the mill                       3.5':Dump at 140° C.                                                   ______________________________________                                         .sup.(1) Flexon ® 876 is paraffinic oil, Exxon Chemical Co.               .sup.(2) MBTS is 2,2benzothiazyl disulfide                               

                  TABLE II                                                        ______________________________________                                                        COMPOSITION                                                   Ingredients       A        B        C                                         ______________________________________                                        Copolymer Z       100                                                         Copolymer Y                100                                                Copolymer X                         100                                       Carbon Black N-660                                                                              60       60       60                                        FLEXON 876        15       15       15                                        STEARIC ACID      1        1        1                                         ZnO               2        2        3                                         SULPHUR           1        1        0.5                                       MBTS              2        2        1.5                                       Copolymer viscosity                                                                             33.4     30.4     32.4                                      ML 1 + 8 125° C.                                                       UNCURED                                                                       COMPOUND PROPERTIES                                                           Mooney Viscosity 100° C.                                                                 45.1     42.8     46.1                                      ML 1 + 4                                                                      Mooney scorch 135° C.                                                  MS t3, mins       10.61    13.66    14.74                                     MS t5, mins       11.65    14.86    16.33                                     MS t10, mins      12.70    16.02    17.95                                     ODR (Monsanto) at 160° C.                                              ODR-ML lbs*inch   6.81     6.01     7.69                                                        (9.23J)  (8.14J)  (10.42J)                                  ODR-MH lbs*inch   35.12    36.01    27.03                                                       (47.60J) (48.79J) (36.60J)                                  ODR-Ts2 minutes   2.93     3.65     3.39                                      ODR-T'50 minutes  4.26     5.32     5.58                                      ODR-Tc'90 minutes 16.96    14.29    12.48                                     ______________________________________                                    

                  TABLE III                                                       ______________________________________                                                       COMPOSITION                                                    Ingredients      A         B        C                                         ______________________________________                                        Copolymer Z      100                                                          Copolymer Y                100                                                Copolymer X                         100                                       Carbon Black N-660                                                                             60        60       60                                        FLEXON 876       15        15       15                                        STEARIC ACID     1         1        1                                         ZnO              2         2        3                                         SULPHUR          1         1        0.5                                       MBTS             2         2        1.5                                       CURED COMPOUND,                                                               ORIGINAL PROPERTIES                                                           PRESS CURE 160° c.                                                                      19'       16'      14'                                       Hardness Shore A 46        48       42                                        Modulus 100% Mpa 1.42      1.78     1.04                                      Modulus 300% Mpa 5.64      6.61     4.16                                      Tensile Strength MPa                                                                           10.75     10.94    9.67                                      Elongation at Break %                                                                          650       585      680                                       MONSANTO FLEX                                                                 RESISTANCE                                                                    140% ext, cam 24                                                              min, kcycles     25.48     7.62     54.33                                     max, kcycles     258.21    97.64    279.04                                    avg, kcycles     128.70    25.34    165.75                                    PRESS CURE 160° C.                                                                      29'       24'      19'                                       PEEL ADHESION, Self                                                                            36/36     37/37    30/30                                     kN/m Min.        11.37     11.18    13.21                                     kN/m Max.        24.57     23.48    36.07                                     Type of failure  Stock     Stock    Stock                                     PRESS CURE 160° C.                                                                      29'       24'      19'                                       PEEL ADHESION.sup.(1)                                                                          36/32     37/32    30/32                                     kN/m             1.16       2.36    5.33                                      Type of failure  Interface Interface                                                                              Interface                                 PRESS CURE 160° C.                                                                      29'       24'      19'                                       PEEL ADHESION.sup.(2)                                                                          36/33     37/33    30/33                                     kN/m             3.52      5.12     8.38                                      Type of failure  Interface Interface                                                                              Interface                                 PRESS CURE 160° C.                                                                      29'       24'      19'                                       PEEL ADHESION.sup.(3)                                                                          36/34     37/34    30/34                                     kN/m             5.59      6.71     11.17                                     Type of failure  Interface Interface                                                                              Interface                                 ______________________________________                                         Footnotes:                                                                    .sup.(1) Adhesion to a chafer compound based on 25/75 natural                 rubber/butadiene rubber.                                                      .sup.(2) Adhesion to a carcass compound based on 50/50 natural                rubber/styrenebutadiene rubber.                                               .sup.(3) Adhesion to a carcass compound based on 100 percent natural          rubber.                                                                  

                  TABLE IV                                                        ______________________________________                                                           COMPOSITION                                                Ingredients          A       B       C                                        ______________________________________                                        Copolymer Z          100                                                      Copolymer Y                  100                                              Copolymer X                          100                                      Carbon Black N-660   60      60      60                                       FLEXON 876           15      15      15                                       STEARIC ACID         1       1       1                                        ZnO                  2       2       3                                        SULPHUR              1       1       0.5                                      MBTS                 2       2       1.5                                      AGED PROPERTIES 3 DAYS at                                                     150° C.                                                                PRESS CURE 160° C.                                                                          19'     16'     14'                                      Hardness Shore A     55      57      49                                       Modulus 100% Mpa     2.00    2.27    1.86                                     Modulus 300% Mpa     7.04    7.50    5.79                                     Tensile strength Mpa 10.85   11.15   6.66                                     Elongation at Break %                                                                              545     520     380                                      MONSANTO FLEX RESISTANCE                                                      140% ext, cam 24                                                              min, kcycles         22.31   8.71    15.79                                    max, kcycles         130.74  35.34   244.37                                   avg, kcycles         76.31   17.44   120.21                                   AGED PROPERTIES 7 DAYS at                                                     150° C.                                                                PRESS CURE 160° C.                                                                          19'     16'     14'                                      Hardness Shore A     56      58      50                                       Modulus 100% Mpa     1.94    2.48    1.96                                     Modulus 300% Mpa     6.89    7.78                                             Tensile Strength MPa 10.92   10.80   5.02                                     Elongation at Break %                                                                              570     485     280                                      AGED PROPERTIES 7 DAYS at                                                     150° C. (Repeated)                                                     PRESS CURE 160° C.                                                                          19'     16'     14'                                      Hardness Shore A     58      60      47                                       Modulus 100% Mpa     2.56    3.16    1.70                                     Modulus 300% Mpa     9.51    10.44   5.10                                     Tensile Strength Mpa 11.72   11.19   5.23                                     Elongation at Break %                                                                              400     335     310                                      Monsanto Flex Resistance                                                      140% ext, cam 24                                                              min, kcycles         15.59   8.56    1.69                                     max, kcycles         80.69   26.97   2.48                                     avg, kcycles         54.48   11.48   2.24                                     AGED PROPERTIES 14 DAYS at                                                    150° C.                                                                PRESS CURE 160° C.                                                                          19'     16'     14'                                      Hardness Shore A     60      64      44                                       Modulus 100% Mpa     2.7     3.7     1.5                                      Modulus 300% Mpa     9.9     --      --                                       Tensile Strength Mpa 10.9    10.8    3.6                                      Elongation at break, %                                                                             340     290     275                                      ______________________________________                                    

                  TABLE V                                                         ______________________________________                                        Property             Test                                                     ______________________________________                                        Mooney Viscosity     ASTM D1646                                               Mooney Scorch        ASTM D4818                                               Oscillating Disc Reheometer                                                                        ASTM D2084                                               (ODR - Monsanto)                                                              Press Cure           ASTM D2240/D412                                          Elongation at break  ASTM D412                                                ______________________________________                                    

As can be seen from the data in Tables I, II, III, and IV, thecompositions in accordance with the present invention, that is,Composition A and B had improved heat aging properties relative tocomparative composition C, particularly for aged flex resistance,tensile strength, and elongation at break, and similar good cureproperties and cured original properties as comparative Composition C.

What is claimed is:
 1. A vulcanized tire comprising an innerliner, atleast a portion of said innerliner comprising a composition comprising:(a) about 40 to about 70 weight percent of a halogen-containing randomcopolymer of a C₄ to C₇ isomonoolefin and a para-alkylstyrene, saidpara-alkylstyrene comprising 0.5 to about 20 weight percent of saidcopolymer, (b) about 20 to about 45 weight percent carbon black; and (c)about zero to about 25 weight percent of a plasticizer oil.
 2. Thevulcanized tire of claim 1, wherein said composition additionallycomprises a component selected from the group consisting of a fillerother than carbon black, a rubber compounding additive and mixturesthereof.
 3. The vulcanized tire of claim 1, wherein said plasticizer oilcomprises a paraffinic oil.
 4. The vulcanized tire of claim 1, whereinsaid copolymer comprises from above 0 to about 7.5 weight percent ofsaid halogen.
 5. The vulcanized tire of claim 1, wherein said halogen isselected from the group consisting of chlorine, bromine, and mixturesthereof.
 6. The vulcanized tire of claim 1, wherein said halogencomprises bromine, and wherein said bromine is chemically bound to saidpara-alkylstyrene.
 7. The vulcanized tire of claim 1, wherein saidisomonoolefin is isobutylene and said para-alkylstyrene ispara-methylstyrene.
 8. The vulcanized tire of claim 2, wherein saidcomponent is a filler, and wherein said filler is selected from thegroup consisting of clay, silica, calcium carbonate, titanium dioxide,and mixtures thereof.
 9. The vulcanized tire of claim 2, wherein saidcomponent is a rubber compounding additive and wherein said rubbercompounding additive is selected from the group consisting ofantioxidants, stabilizers, pigments, and mixtures thereof.
 10. Thevulcanized tire of claim 2, wherein said component is a rubbercompounding additive and wherein said rubber compounding additive isstearic acid.
 11. The vulcanized tire of claim 1, wherein saidcomposition additional comprises a rubber component selected from thegroups consisting of natural rubber, polybutadiene rubber,styrene-butadiene rubber, a terpolymer of ethylene, propylene, and anonconjugated diene, and mixtures thereof.
 12. The vulcanized tire ofclaim 1, wherein said tire is a motor vehicle tire.